The invention relates to the field of intravascular guiding members. In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is advanced in the patient""s vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. Conventional guidewires for angioplasty and other vascular procedures usually comprise an elongated core member with one or more tapered sections near the distal end thereof and a flexible body such as a helical coil disposed about the distal portion of the core member. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient""s vascular system.
A major requirement for guidewires and other guiding members is that they be flexible enough to avoid damaging the blood vessel or other body lumen through which they are advanced. However, they also must have sufficient column strength to be pushed through a patient""s vascular system or other body lumen without kinking. These characteristics are especially difficult to achieve when designing guidewires capable of crossing relatively tight lesions, particularly with chronic total occlusions (CTO""s). Conventional guidewires typically do not have distal tips capable of crossing such lesions.
Accordingly, there is a need for guidewire designs that facilitate the crossing of relatively tight lesions without sacrificing handling characteristics. The present invention satisfies these and other needs.
The present invention is directed to a guidewire or other guiding member having a tapered distal coil. Generally, the guidewire comprises an elongated core member having a proximal section and a distal section and a coil disposed about and secured to the distal core section. The coil has a distal portion which tapers distally to the distal end thereof. At least part of the tapered distal portion of the coil is provided with a polymer coating which bridges or encapsulates individual turns of the coil.
The polymer coating covers the coil a distance of at least about 1.5 cm and may extend the entire length of the coil, e.g. up to a distance of about 40 cm from the distal end of the coil and preferably a distance of about 2 to about 12 cm from the distal end of the coil. The polymer coating has a thickness of about 0.0001 inch to 0.004 inch (0.0025 mm to 0.1 mm).
The outer diameter of the distal portion of the coil may taper from about 0.001 inch to 0.035 inch (0.0025 cm to 0.089 cm), to an outer diameter of about 0.006 inch to about 0.02 inch (0.15-0.51 mm), preferably about 0.008 inch to about 0.014 inch (0.2-0.36 mm). The tapered portion of the coil is about 1 cm to about 10 cm in length, preferably about 2 to about 5 cm in length. The entire coil length may range from about 3 to about 40 cm, preferably about 10 to about 30 cm.
The tapered coil, particularly with the polymer coating which bridges or encapsulates the turns of the coil, facilitates advancement through tight lesions such as CTO""s. The polymer coating provides a smoother surface than the coil turns alone, and fixes the turns of the coil for a more damage tolerant distal tip.
These and other features of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.